You can create a table map that can be used to mark traffic attributes. A table map is a kind of two-way conversion chart that lists and maps one traffic attribute to another. A table map supports a many-to-one type of conversion and mapping scheme. The table map establishes a to-from relationship for the traffic attributes and defines the change to be made to the attribute. That is, an attribute is set to one value that is taken from another value. The values are based on the specific attribute being changed. For instance, the Precedence attribute can be a number from 0 to 7, while the DSCP attribute can be a number from 0 to 63.
The following is a sample table map configuration:
table-map table-map1
map from 0 to 1
map from 2 to 3
exit
The table below lists the traffic attributes for which a to-from relationship can be established using the table map.
Table 2 Traffic Attributes for Which a To-From Relationship Can Be Established
The "To" Attribute |
The "From" Attribute |
Precedence |
CoS |
QoS group |
DSCP |
CoS |
QoS group |
CoS |
Precedence |
DSCP |
QoS group |
Precedence |
DSCP |
MPLS EXP topmost |
MPLS EXP topmost |
QoS group |
MPLS EXP imposition |
Precedence |
DSCP |
Once the table map is created, you configure a policy map to use the table map. In the policy map, you specify the table map name and the attributes to be mapped by using the table keyword and the table-map-name argument with one of the commands listed in the table below.
Table 3 Commands Used in Policy Maps to Map Attributes
Command Used in Policy Maps |
Maps These Attributes |
set cos dscp table table-map-name |
CoS to DSCP |
set cos precedence table table-map-name |
CoS to Precedence |
set dscp cos table table-map-name |
DSCP to CoS |
set dscp qos-group table table-map-name |
DSCP to qos-group |
set mpls experimental imposition dscp table table-map-name |
MPLS EXP imposition to DSCP |
set mpls experimental imposition precedence table table-map-name |
MPLS EXP imposition to precedence |
set mpls experimental topmost qos-group table table-map-name |
MPLS EXP topmost to QoS-group |
set precedence cos table table-map-name |
Precedence to CoS |
set precedence qos-group table table-map-name |
Precedence to QoS-group |
set qos-group dscp table table-map-name |
QoS-group to DSCP |
set qos-group mpls exp topmost table table-map-name |
QoS-group to MPLS EXP topmost |
set qos-group precedence table table-map-name |
QoS-group to Precedence |
The following is an example of a policy map (policy2) configured to use the table map (table-map1) created earlier:
policy map policy2
class class-default
set cos dscp table table-map1
exit
In this example, a mapping relationship was created between the CoS attribute and the DSCP attribute as defined in the table map.